My 2yr old has a bad cough and kind of strains when he coughs. what should i do?

Take him to doctor.: If he is having that much trouble when he coughs, his doctor needs to see him to make sure it's not something more severe that a common cold.

See your doctor: A bad cough with straining needs to be evaluated. We want to make sure your child is not wheezing or has bronchitis or worse. Once that has happened, we have a better idea of what to do. I know of some great chinese herbaceuticals and homeopathic remedies for cough, but i would want to evaluate a cough like you describe first.